[POWERPC] Fix PCI IRQ fallback code to not map IRQ 0

The PCI IRQ code has a fallback when the device-tree parsing fails, that
tries to map the interrupt indicated by PCI_INTERRUPT_LINE if the firmware
set something in there. This is a bit fragile but has proven useful in some
cases so far. However, it's causing us to incorrectly try to map interrupt 0
on various setups, so let's prevent that case, as none of the cases where
the fallback is legit should have an IRQ 0.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index 88838b0f8b90..571854f2906c 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -225,10 +225,11 @@ int pci_read_irq_line(struct pci_dev *pci_dev)
                 if (pin == 0)
                         return -1;
                 if (pci_read_config_byte(pci_dev, PCI_INTERRUPT_LINE, &line) ||
-                    line == 0xff) {
+                    line == 0xff || line == 0) {
                         return -1;
                 }
-                DBG(" -> no map ! Using irq line %d from PCI config\n", line);
+                DBG(" -> no map ! Using line %d (pin %d) from PCI config\n",
+                    line, pin);
 
                 virq = irq_create_mapping(NULL, line);
                 if (virq != NO_IRQ)